The sensors of this type normally consist of a transformer comprising a primary circuit to which is supplied an alternating current and two secondary circuits in which a ferromagnetic part in linear motion generates signals, the demodulation of which will enable the measurement of the displacement of the moving part to be acquired. These sensors and their conditioning electronics can have numerous applications: monitoring works of art, monitoring the production of mechanical parts, measuring the level of a liquid in tanks, monitoring the position of vehicle controls, for example a motor vehicle, a ship or an aircraft. The processing of the signal can differ according to the accuracy and the reliability sought for a given application.
One of the main problems is the phase shift that appears between the signals of the two secondaries which affects the accuracy of the measurement when a conventional synchronous demodulation is applied. One of the known responses is to use transformers with guaranteed phase shift tolerance. However this adds significantly to the cost of the LVDTs, which can be prohibitive in the case of acquisition subsystems with several tens of LVDTs which are commonly used in aeronautics.